Process for stabilizing furnace oil



Patented Sept. 23, 1958 fiice PROCESS FOR STABILIZING FURNACE OILRussell H. Brown, Hammond, Ind., assignor to Standard Oil Company,Chicago, 111., a corporation of Indiana No Drawing. Application February10, 1955 Serial No. 487,443 7 Claims. (Cl. 196-29) This inventionrelates to a stabilized hydrocarbon oil boiling in theheavier-than-gasoline range, which oil has been derived from a catalyticcracking operation. More particularly, the invention relates to afurnace oil which contains a catalytically cracked oil which has beenstabilized by the process of the invention.

Oils boiling in the heavier-than-gasoline range, i. e., between about350 F. and about 600 P. which have been obtained from the liquid productof the catalytic cracking of hydrocarbon oils, are of unsatisfactorystorage stability as determined by deterioration in color formation ofgums and sediments. When catalytically cracked oils boiling in thisdistillate fuel range are mixed with virgin oils which boil in thedistillate fuel range, which virgin oils have been sweetened by theDoctor method, the resulting blend is much less stable than either ofthe components alone. This characteristic is known as incompatibility ofstocks. The demnad for hydrocarbon oils for use in domestic furnaces hasincreased so markedly in recent years that the demand cannot be suppliedby a 100% virgin gas oil material. Therefore, it is necessary that astable blended furnace oil be producible by the refiner.

An object of the invention is a method for stabilizing oils boiling inthe heavier-than-gasoline range which have been derived from catalyticcracking operations. Another object is a catalytically cracked gas oilboiling in the heavier-than-gasoline range which has satisfactorystorage stability with respect to gum, sediment and color. Still anotherobject is a method of producing a furnace oil of good storage stability,which furnace oil is made by blending a Doctor sweentened virgin gas oiland a catalytically cracked cycle oil. A particular object is a furnaceoil of satisfactory storage stability with respect to color, gum andsediment, which furnaces oil is made by blending a Doctor sweetenedvirgin gas oil and a catalyically cracked cycle oil.

A raw sour oil derived from a catalytic cracking operation, which oilboils in the heavier-than-gasoline range, is stabilized with respect tothe color, gum and sediment by adding to the raw oil between about 0.001and about 0.004 weight percent of an alkali-metal hydroxide and betweenabout 0.0005 and about 0.002 weight percent of free iodine. A furnaceoil of improved stability with respect to color, gum and sediment isproduced by blending a catalytically cracked oil treated by the aboveprocess and a virgin gas oil which has been sweetened by the Doctormethod.

The catalytically cracked oil charged to the treating process boils inthe range of about 350 F. and 650 F. This oil has been derived from theconversion products of the catalytic cracking of heavier hydrocarbonoils, such as gas oils and reduced crudes. In the refining operation,these catalytically cracked oils are known as catalytic cycle stocks.The catalytic cracking operation which produces the catalyticallycracked oil charged to the treating process of the invention may be anyone of the wellknewn processes now in use in the petroleum industry,

for example, the fluidized catalytic cracking process, the thermoforcatalytic cracking process, the Houdriflow cracking process, the Houdrycatalytic cracking process, or the cycloversion process.

The catalytically cracked oil should be treated immediately after it iswithdrawn from the fractionator or stored in intermediate storage whichis equipped to prevent contact of air of free-oxygen with the raw oil.Hereinafter the term raw oil means the sour catalytically cracked oil asit has been withdrawn from the fractionator without immediate storage tothe treating process or has been stored without contact with atmosphericoxygen. Frequently the raw oil as produced contains entrained water asis evidenced by the presence of a haze. The presence of entrained wateras evidenced by a heavy haze has an adverse effect on the quality of thetreated oil and therefore it is preferred that the raw oil be freed ofentrained water, if any is present. This may be done by prolongedsettling in the absence of oxygen, or passing the oil through acoalescer such as a fibre glass packed vessel or through a salt drum.

The raw oil is treated to render it more stable by adding to the raw oilbetween about 0.001 and about 0.004 weight percent of an alkali-metalhydroxide, such as sodium hydroxide or potassium hydroxide. It has alsobeen found that alkali-metal phenolates may be added to the oil toobtain the desired result. The amount of sodium or potassium phenolatewhich is added should be substantially equivalent to the above definedamounts of metal hydroxide. Addition of appreciably less than 0.001weight percent of alkali-metal hydroxide is relatively ineffective forstabilizing the oil and the addition of appreciably more than 0.004weight percent of alkalimetal hydroxide results in the formation of aseparate phase of alkali-metal hydroxide. The alkali-metal hydroxide ispreferably added to the oil in the form of a concentrated solution in asubstantially anhydrous alcohol. For example, methanol, ethanol andisopropanol. The alkali-metal hydroxide may be added to the raw oil inthe form of a saturated aqueous solution; this is particularly so whenthe addition is carried out at a relatively high temperature, such asl50200 F.

The treating process includes not only the addition of the above-definedamounts of alkali-metal hydroxide but also the addition of between about0.0005 and about 0.002 weight percent of free-iodine. (A compound whichreadily decomposes to produce free-iodine, such as sodium iodate, may beused.) The iodine is preferably added in the form of an alcoholicsolution. Use of appreciably less than 0.0005 weight percent offree-iodine is relatively ineffective and the use of appreciably morethan about 0.002 weight percent may have a deleterious effect on thestability of the treated oil.

The treating operation may be carried out at ordinary temperatures oreven at moderately elevated temperatures. Thus the process may becarried out between about 30 F. and 250 F or even somewhat higher.Normally, the treating operation will be carried out at the temperatureat which the catalytically cracked oil is produced from thefractionator. Typically, this is on the order of F.

It has been found that the treated oil which is very sour, as determinedby the Doctor test, as produced, and immediately after having beentreated, gradually becomes sweet with open exposure to free-oxygen. Whenadequate storage space is available, the sweetening may be obtained bysimply allowing the treated oil to remain in a tank which is vented tothe atmosphere for 2 to 4 days. More rapid sweetening can be obtained byadding free-oxygen to the treated oil, for example, by injectingcylinder oxygen into the stream of treated oil as it passes to thestorage tank.

Presently the higher quality distillate fuels used in iomestic furnaces,i. e., furnace oils, are blends of cracked oils and virgin oils.Typically the virgin oil component is a gas oil boiling in the range ofabout 350 F. and 650 F. The virgin gas oil component has been made sweetto the Doctor test usually by the well-known Doctor method. In thismethod, the sour oil is contacted with an aqueous plumbite solution inthe presence of freesulfur and air until the oil is sweet as determinedby the Doctor test. Usually the refiner uses as the virgin component 2,or even more, different virgin gas oils,

different in the sense of boiling range primarily.

Generally the furnace oil consists of not more than about 70 parts ofcatalytically cracked oil and about 30 parts of the Doctor-sweetenedvirgin gas oil. Generally the furnace oil consists of at least aboutparts of catalytically cracked oil and about 80 parts of Doctorsweetenedvirgin gas oil.

The effectiveness of the treating process of this in- .vention instabilizing catalytically cracked oils and overcoming incompatibilitywith Doctor-sweetened virgin oils, is illustrated by the followingtests.. In these tests, the catalyically cracked oil was a lightcatalytically cracked oil (LCCO) which boiled over the range of 350 F.to 550 F. This oil had been produced by the fluidized catalyticcracking, using a silica alumina catalyst, of high sulfur virgin gasoils. The virgin gas oil component of the furnace oil tested was derivedfrom two sources. The virgin component boiled over the range of 350 to650 F. The virgin component had been sweetened by contacting it with 4volume percent of Doctor solution and 150% of the theoretical offree-sulfur. The Doctor solution contained water, sodium hydroxide, andsodium plumbite; the lead content was about 1.7 grams, as PbO, per 100ml. of solution. The furnace oil consisted of a blend of 32 volumes ofLCCO and 68 volumes of Doctor-sweetened virgin oil. Four furnace oilswere made up wherein the LCCO portion was given either no treatment ortreated as follows: The raw, sour oil obtained directly from thefractionator had added to it 0.002 weight percent of sodium hydroxide asa concentrated solution in anhydrous methanol; another portion of raw,sour oil had added to it 0.001 weight percent of free-iodine as analcohol solution; another portion of the raw oil had added to it bothsodium hydroxide and freeiodine0.002 weight percent of sodium hydroxideand 0.001 weight percent of free-iodine. Two different batches of eachfurnace oil were produced in order to enable testing of the differentfurnace oils after 3 months and 6 months, respectively, of storage invented bottles. The storage was at about 90 F.

The comparisons between the furnace oils were made on the basis of theNPA color of the oil, the acid floc gum and sediment. Both gum andsediment were determined as mg. per 100 ml. of oil by the technique ofProell and Bolt, Oil and Gas Journal, March 30, 1946.

TEST 1 The four different oils were inspected after 3 months of storagein vented bottles and the results of these tests are set out in Table Ibelow.

4 TEST 2 The oils were again inspected after 6 months of storage. Theresults of these tests are set out in Table II below.

The above data show that a remarkable improvement in stability withrespect to color, gum and sediment is obtained by treating thecatalytically cracked portion of the furnace oil according to theprocess of this invention. In every respect the oil containing LCCOtreated with both sodium hydroxide and free-iodine was better than thefurnace oils which had been treated with only one of the two componentsof the treating processes. It is submitted that these data show that theobjects of the invention have been attained.

Thus having described the invention, what is claimed 1. A process forproducing a sweet, storage-stable furnace oil which process comprises(A) (i) removing entrained water, immediately subsequent to theproduction thereof and before any contact with atmospheric oxygen, froma liquid sour oil boiling in the range of about 350 F. and about 650 R,which oil has been produced by the catalytic cracking of a petroleum oiland (ii) dissolving in said dewatered oil between about 0.001 and about0.004 weight percent of alkali-metal hydroxide, and between about 0.0005and about 0.002 weight per cent of free-iodine, based on said dewateredoil, respectively, (B) contacting a sour virgin gas oil obtained bydistillation of petroleum, which oil boils in the range of about 350 F.and about 650 F., with aqueous plumbite in the Doctor method andseparating a sweet gas oil from aqueous solution, (C) blending saidalkali-metal hydroxide and free-iodine containing-oil and said sweet gasoil in a volume ratio of said oil and said sweet gas oil between about20:80 and :30, said blend being sour to the Doctor test, and (D)exposing said blend to freeoxygen for a time sufiicient to produce asweet furnace oil which is storage-stable.

2. The process of claim 1 wherein said alkali-metal hydroxide is addedto said dewatered oil in the form of a saturated aqueous solution.

3. The process of claim 1 wherein said alkali-metal hydroxide is addedto said dewatered oil in the form of a solution in anhydrous methanol.

4. The process of claim 1 wherein said free-iodine is added to saiddewatered oil in the form of an alcohol solution.

5. The process of claim 1 wherein said blend is composed of about 32volumes of said oil and about 68 volumes of said sweet gas oil.

References Cited in the file of this patent UNITED STATES PATENTS MillerAug. 31,

1. A PROCESS FOR PRODUCING A SWEET, STORAGE-STABLE FURNACE OIL WHICHPROCESS COMPRISES (A) (I) REMOVING ENTRAINED WATER, IMMEDIATELYSUBSEQUENT TO THE PRODUCTION THEREOF AND BEFORE ANY CONTACT WITHATMOSPHERIC OXYGEN, FROM A LIQUID SOUR OIL BOILING IN THE RANGE OF ABOUT350* F. AND ABOUT 650*F., WHICH OIL HAS BEEN PRODUCED BY THE CATALYTICCRACKING OF A PETROLEUM OIL AND (II) DISSOLVING IN SAID DEWATERED OILBETWEEN ABUT 0.001 AND ABOUT 0.004 WEIGHT PERCENT OF ALKALI-METALHYDROXIDE, AND BETWEEN ABOUT 0.0005 AND ABOUT 0.002 WEIGHT PERCENT OFFREE-IODINE, BASED ON SAID DEWATERED OIL, RESPECTIVELY, (B) CONTACTING ASOUR VIRGIN GAS OIL OBTAINED BY DISTILLATION OF PETROLEUM, WHICH OILBOILS IN THE RANGE OF ABOUT 350*F. AND ABOUT 650*F., WITH AQUEOUSPLUMBITE IN THE DOCTOR METHOD AND SEPARATING A SWEET GAS OIL FROMAQUEOUS SOLUTION, (C) BLENDING SAID ALKALI-METAL HYDROXIDE ANDFREE-IODINE CONTAINING-OIL AND SAID SWEET GAS OIL IN A VOLUME RATIO OFSAID OIL AND SAID SWEET GAS OIL BETWEEN ABOUT 2:80 AND 70:30, SAID BLENDBEING SOUR TO THE TEST, AND (D) EXPOSING SAID BLEND TO FREEOXYGEN FOR ATIME SUFFICIENT TO PRODUCE A SWEET FURNACE OIL WHICH IS STORAGE-STABLE.